Trolling attachment for motorboats



A. J. MCGRETE 2,226,007

TROLLING ATTACHMENT FOR MOTORBOATS Dec. 24, 1940.

Filed Oct. 9, 1939 IN VEN TOR. ALBERT J/V/a G057:

C a/ca/z/QM' ATTORNEY.

Patented Dec. 24, 1940 UNITED STATES TROLLING ATTACHMENT FOR MOTOR- BOATS Albert J. McGrete, Oakland, Calif., assignor to Bernhard Kilian, Alameda, Calif.

Application October 9, 1939, Serial No. 298,567

4 Claims.

This invention relates generally to means for slowing a motorboat to a speed suitable for trolling or other purposes and is more particularly directed to a device which may be detachably applied to the free end of a propeller shaft adjacent the propeller.

It is the principal object of the present invention to provide a device capable of being mounted on the propeller shaft adjacent the propeller to 10 rotate therewith and functioning to reduce the driving eifect produced by the propeller without materially affecting its speed of rotation, so as to retard the boat to a speed below that which would be attained by such speed of propeller 15 rotation were said device not present, and to provide a device of this character which may be quickly and easily applied to or detached from the propeller shaft without the use of tools or other assisting devices.

20 One form which the invention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawing, in which:

Fig. l is an end elevation, partly broken away,

25 of the device of the present invention as applied to the propeller shaft upon which the propeller is mounted.

Fig. 2 is a vertical section taken on the line IIII of Fig. 1, showing the propeller in eleva- 30 tion.

Fig. 3 is a detail perspective view of the fitting which forms a part of the invention.

In the use of relatively small motorboats for fishing, and particularly for trolling, a relatively slow boat speed is required, whereas a boat of this character is ordinarily propelled by a relatively small high speed propeller driven by a high speed motor, either of the inboard type or of the outboard type, having a relatively high, minimum or idling speed which will produce a normal boat speed much too fast for trolling purposes and which cannot be throttled down to trolling speed without stalling the motor.

It is in such situations that the present inven- 45 tion will have exceptional utility in providing a means for retarding or reducing the driving effect produced by the high speed propeller without reducing the rotative speed of the propeller and motor to a degree which may stall the motor.

50 In the illustrated embodiment, the propeller III is shown mounted on the usual propeller shaft I I and in Fig. '2 said shaft is illustrated as being of the type usually employed in connection with outboard motors and having an externally screwthreaded free end Ila.

In a standard installation the propeller I is retained on the propeller shaft I I by a castellated nut. However, in the installation of the device of the present invention, the nut of the standard installation will be replaced by an elongated fitting I2 of the character illustrated in Fig. 3.

Preferably, the fitting I2 will be formed from a bar of hexagon stock and machined to provide near its outer end on annular exterior groove I3, its inner end being axially bored and internally 1o screw-threaded as at I4 and provided with transverse apertures I5 to accommodate a looking or cotter pin I6. This elongated fitting I2 will be screwed on the shaft end Ila to retain the propeller III in place, and a cotter pin It will be threaded through a transverse pair of the apertures I5 and through an aligned transverse bore in said shaft end and then bent over in the usual manner to prevent/accidental loosening of said fitting. Said fitting thus forms a removable continuation of the propeller shaft and is rotatable therewith.

The speed retarding element comprises a relatively thin circular disc I! which is detachably supported on the free end of the fitting I2 to the rear of and closely adjacent the propeller III, as shown in Fig. 2, and for this purpose said disc I! is provided with an axially disposed central opening or bore I8 extending through its hub portion I9 and of a hexagonal shape comparable in size and form to the cross-sectional contour of the elongated hexagonal nut or fitting I2. The disc I1 is in this manner slidably splined on the fitting I2 to rotate therewith. The hub portion I9 of said disc I1 is also provided with a transverse bore 20 intersecting the axial bore I8 of the disc and formed to provide a spring abutment shoulder 2I. In this transverse bore 20 is slidably disposed a latch plunger 22 having a stem 23 of reduced diameter which extends to the exterior and is there provided with an actuating knob 24, a coil spring 25 surrounding the stem 23 of said latch plunger between the head thereof and the abutment shoulder 2| and normally exerting its tension to yieldingly maintain said plunger engaged in the groove I 3 of the fitting I2, as shown in Figs. 1 and 2.

In the use of the illustrated device, the fitting I2, which serves not only to maintain the propeller III on its shaft II but also as a means for supporting and for rotating the retarding disc II, may remain mounted on the propeller shaft and the motor may be operated to drive the boat in the usual manner.

When it is desired to operate the boat at slow speed for trolling, the motor will be stopped so that the retarding or trolling disc I! may be applied to the fitting II. This will beaccomplished by manually holding the latch plunger 22 re- 5 tracted against the tension of its spring 25, while the disc I] is slid over the free end of the fitting I2, and then releasing said plunger to enga e in the groove I 3 thereof. On an outboard motor this will preferably be done while the motor is swung to elevate its propeller above the water,

while in an inboard motor installation it will be accomplished by reaching into the water. In

either case the application or the removal of the retarding or trolling disc or plate H can be 16 easily and quickly accomplished by reason of the fact that no tool or like device is needed for the purpose.

It is to be noted that the diameter of the disc I] is somewhat less than that of the propeller a blades, due to which fact the tip portions of said blades maintain, to a large degree, their normal propelling ei'llciency. However, it will be \mderstood by those skilled in the art that the presence of the adjacent trolling plate I! will eifectively 3| diminish the total propelling eiilciency of the propeller, not only by spreading the propelling effort but also by acting as a drag, the retarding eifect being adequate to slow the boat to a speed suitable for trolling. From the foregoing it will be understood that the present invention involves the provision of a fitting capable of being removably secured on the free end of a propeller shaft and having a latch groove or element, and a speed retarding so element or trolling disc slidably splined on said fitting by a manually actuated latch means and in a manner permitting easy and quick assembling thereon or removal therefrom without the use of tools or other assisting devices and by persons entirely unskilled in mechanics or the use of tools. 7

While I have shown the preferred form of my invention it is to be understood that various changes may be made in its construction by those 45 skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A trolling attachment adapted for cooperation with a mounted propeller and comprising an axial fitting adapted to be secured to the free end of the propeller shaft to form an extension 5 thereof and provided with an external latch groove, a speed retarding trolling disc axially slidable on said fitting for removal therefrom and splined thereon for rotation therewith, and a spring-pressed latch on said disc adapted to 10 engage in said latch groove to maintain said disc against accidental displacement from said fitting and manually releasable from such engagement to release said disc for removal from said fitting. l5

2. A trolling attachment for a propeller shaft having a screw-threaded end. said attachment comprising an axial fitting in the form of an elongated nut adapted for screw-threaded engagement on said shaft end to form an extension 20 of said propeller shaft, said fitting having formed therein an external latch enga in groove, a speed retarding trolling disc axially slidable on said fitting for removal therefrom, the axial bore of said disc having a cross-sectional contour 2 comparable to the cross-sectional shape of said fitting whereby said fitting and disc will be splined for unitary rotation, and a spring-pressed latch plunger on said disc adapted to engage in said latch groove to maintain said disc on said fitting and manually releasable from such engagement to release said disc for removal from said fitting.

3. A speed retarding trolling disc having a non-circular axial bore and a transverse bore intersecting said axial bore, a latch plunger slidably disposed in said transverse bore for limited movement therein, and a spring tending to proiect the inner end of said plunger into said axial bore, said plunger having an outer end extend- 0 ing from said transverse bore whereby the plunger may be manually retracted.

- 4. A speed retarding trolling disc having an axial bore and provided with a spring-pressed latch means normallyv projecting into said bore and capable of manual withdrawal therefrom.

' ALBERT J. MCGRETE. 

